1. Field of the Invention
The present invention relates to a technique for an electric storage device, and more particularly to a technique that is effective when applied to a lithium electrode.
2. Description of the Related Art
A lithium ion secondary battery or the like is available as an electric storage device installed in an electric automobile, a hybrid automobile, and so on (an EV and so on). To improve an energy density of the electric storage device, electric storage devices having a lithium electrode into which lithium metal is incorporated as an ion supply source have been proposed (see Japanese Patent No. 3485935 and WO 2004/059672, for example). In these electric storage devices, lithium metal is electrochemically connected to a negative electrode or a positive electrode such that lithium ions from the lithium metal are doped in advance (pre-doped). These electric storage devices are provided with the aim of achieving further improvements in capacity and other cell characteristics in order to extend a travel distance of an EV or the like.
However, when lithium ion pre-doping is performed in a lithium ion pre-doping type electric storage device, the pre-doping is not performed evenly due to variation in conditions such as an electrode surface state, a separator structure, and a cell structure, and as a result, a reliability of the device, and in particular a cycle characteristic, are adversely affected. It is therefore desirable to improve the cycle characteristic by performing pre-doping evenly.